Off-road equipment such as tractors, bulldozers, and other construction equipment, are frequently subjected to dusty conditions which can cause premature clogging of the air pre-cleaner for the engine. To aid in removing accumulations of dust and other solid particles from the pre-cleaner and thereby prevent premature clogging, aspirating mufflers have been utilized. With an aspirating muffler, the flow of exhaust gas through the muffler creates an aspirating action which acts through an aspirating tube to draw dust and other particles from the air cleaner and discharge the dust and particles through the muffler to the atmosphere.
In a common aspirating muffler, exhaust gas from the engine is introduced into the muffler body through an inlet pipe and is discharged from the body through a separate discharge pipe. A venturi is formed in the outlet pipe, and an aspirating tube, which is connected to the pre-cleaner, communicates with the venturi. With this arrangement, flow of exhaust gas through the venturi will create an aspirating action to draw dust and solid particles from the pre-cleaner and discharge the material to the atmosphere.
The venturi, as used in a conventional aspirating muffler, is normally a weldment composed of a converging cone and a diverging cone. The tooling required for forming the conical sections of the venturi is expensive as is the fabrication cost for welding the conical sections to form the venturi. Because of this, the venturi is a significant factor in the overall cost of the aspirating muffler.